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    <script>
        // 生成器就是一个特殊的函数
        //  异步编程  纯回调函数   node fs  ajax  mongodb
        //   yield 函数代码的分隔符
        function * gen(){
            // console.log('111');
            yield '一直没有耳朵';
            // console.log('222');
            yield '一直没有尾巴';
            // console.log('333');
            yield '真奇怪';
            // console.log('444');
        }
        let iterator = gen();
        // console.log(iterator);
        console.log(iterator.next());  
        console.log(iterator.next());
        console.log(iterator.next());
        console.log(iterator.next());  

        // 遍历
        for(let v of gen()){
            console.log(v);
        }
    </script>
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